Differential effects of cadmium on blood lymphocyte subsets

This work was designed to analyze the possible dose dependent effects of cadmium on the blood lymphocyte subset distribution and if these effects are related to circulating cadmium concentration. For that purpose, adult male rats were exposed for one month to 0, 5, 10, 25, 50 or 100 ppm of cadmium chloride (CdCl2) in the drinking water. B lymphocytes decreased in peripheral blood with the doses of 5 and 10 ppm of CdCl2. From the dose of 25 ppm on, B cells increased. T lymphocytes were increased with the doses of 25, 50 and 100 ppm of CdCl2. The lower doses of the metal induced opposite effects. CD4+ and CD8+ cells decreased with the doses of 5 and 10 ppm whereas they were increased with the dose of 25 ppm of CdCl2 on. From the dose of 10 ppm on, cadmium concentration was increased. The results on the distribution of blood lymphocyte subsets suggest that cadmium inhibits the humoral and cellular immune response with the lower doses of the metal used, and opposite effects were detected with the higher doses, the effect not being dependent on the circulating cadmium.     

Estimation of lymphocyte subsets and cytokine levels in workers occupationally exposed to cadmium

IntroductionOccupational exposure to Cadmium (Cd) may have serious health effect on workers. However, little is known about its effect on immune system. Moreover, previous studies have been inconclusive in stating the effect of Cd on immune system. The aim of our study was to estimate immune parameters in workers occupationally exposed to Cd.Material and methods110 individuals occupationally exposed to Cd and 97 apparently healthy non-exposed individuals were recruited for this study. Blood Cadmium levels were determined by AAS. Lymphocyte subset were analyzed using flow cytometry and the cytokine levels were determined by ELISA.ResultsExposed group have significantly higher levels of B-Cd. % of CD8 cells were higher in exposed while % of CD4 cells showed a decreasing trend in the exposed group. Among the CD3CD4 T cell subsets Th1 (%) and Tregs (%) cells were lower while Th17 (%) were higher in exposed group. Increased levels of IL-4 (Th2), IL-6 (Th2) and TNF- α (Th1) and decreased levels of IL-2 (Th1) and IL-10 (Tregs) were observed in Cd exposed workers which is indicative of a predominant pro-inflammatory response in Cd exposed workers. IL-17 (Th17) levels did not show any significant difference between the two groups. Increased Th17/Tregs ratio in the exposed group is also suggestive of an increased pro-inflammatory immune response in exposed group.ConclusionTo conclude, even low level of exposure to Cd in occupational settings is associated with alterations in Th17 cells, which may further predispose an individual to other systemic abnormalities.     

Effect of thymus polypeptide fractions on the development of rat thymus and spleen in organ culture

Peptides of the thymus--vilon, thymogen and thymalin, alone or in combination with concanavalin A, were used to investigate their effect on organotypic culture of thymus and spleen explants from 1- and 21-day old rats. Vilon, thymogen and thymalin in concentrations of 2 and 10 ng/ml and 5 ng/ml, resp., exerted stimulating effects in thymus and spleen tissue cultures from 21-day old rats as compared to the control explants. Vilon and thymogen showed inhibiting effect in the thymus tissue cultures from 1-day old rats as compared to the control explants. However, the peptides together with concanavalin A in concentration of 10 mkg/ml resulted in decreasing the action of concanavalin A alone. The polypeptide fractions of thymus and their synthetic analogs play different roles in the regulation of thymus and spleen development in rats of different age.     

Cellular distribution of prothymosin alpha and parathymosin in rat thymus and spleen

By means of immunohistochemical methods, we have investigated the cellular distribution of prothymosin alpha and parathymosin in rat thymus and spleen, using specific antibodies raised against thymosin alpha-1 and against parathymosin. We observed prothymosin alpha immunoreactivity in lymphoid cells both in thymus and spleen. In the thymus, prothymosin alpha staining was more marked in cortex than in medulla. In the spleen, prothymosin alpha was found in lymphocytes of the periarteriolar lymphatic sheaths and was especially prominent in the germinal centers. Parathymosin immunoreactivity in the thymus was mainly localized in the medulla; positive cells were reticuloepithelial cells from the thymic reticulum and the blood barrier. Thymocytes were negative. In spleen, parathymosin was found in reticular cells arranged in a ring between the periarteriolar lymphatic sheath and the marginal zone. Our results do not support an exclusive role for these peptides as immune system hormones or cytokines.     

Effect of neonatal spleen and thymus implants on H-Y incompatible skin grafts

The transplantation reactivity of adult splenectomized C57BL females to H-Y incompatible skin grafts was significantly reduced by the implantation of spleen and thymus from foetal or 0-1-day-old syngeneic female donors. The thymus implant served as a possible source of natural suppressor cell precursors and the spleen implant as a microenvironment for their maturation.     

Effect of controlled antigenic stimulation on lymphocyte subsets in pigs and pig fetuses

The effect of controlled antigenic stimulation in immunologically virgin organisms,i.e. pig fetuses treated with NDCM (Nocardia delipidated cell mitogen) and germ-free (GF) piglets associated with a non-pathogenicE. coli O86, on peripheral blood lymphocyte subsets defined by the expression of CD5 and CD8 was studied by double color flow cytometry. Stimulation of both fetuses and GF piglets increased the frequency of CD8^low+ lymphocytes. A prominent subset of CD5⁻ CD8^low+ NK cells was present in GF andE. coli associated piglets and their frequency was slightly higher inE. coli associated animals. The most pronounced difference between stimulated and non-stimulated animals was in a relative proportion of an ill-defined lymphocyte subset with an unusual CD5^low+ CD8^low+ expression. Both NDCM injection into fetal blood circulation and association of GF piglets withE. coli resulted in a marked increase of frequency of CD5^low+ CD8^low+ lymphocytes in peripheral blood.     

Effect of cortisone in delineating thymus cell subsets in advanced age.

The mixed lymphocyte reactivity of thymus cells from normal and cortisone-treated, young and old C57BL/6J mice was evaluated. The results indicated that while in the young mice cortisone treatment caused a 12-fold increase in the reactivity of thymus cells, it had no effect on the response of thymus cells from old mice. The significance of the disappearance of cortisone-resistant mature thymus cells in old mice is discussed regarding the general decline in immunocompetence and the increase of autoimmune manifestations in old age.     

Epinephrine-induced changes in the distribution of lymphocyte subsets in peripheral blood of humans

We have previously demonstrated that mitogen responsiveness of mononuclear cells (MNC) from peripheral blood is reduced after a single injection of epinephrine to human subjects. The purpose of the present study was to characterize the relative distributions of MNC subsets after epinephrine administration using monoclonal antibodies and conventional cell markers. The absolute number of circulating MNC increased 64% within 30 min after injection of epinephrine, and returned to baseline by 2 hr. Analysis of MNC subsets revealed that there were no changes in the relative percentages of total T lymphocytes [T3+ cells, or neuraminidase-treated sheep red blood cell rosettes (EN-rosettes)], B lymphocytes (B1+, or cells with surface-bound immunoglobulin), or monocytes (by morphologic criteria) after epinephrine administration. The percentage of inducer T cells (T4+) declined at 30 and 60 min postinjection. Overall, the percentage of suppressor/cytotoxic T cells (T8+) did not change after injection of epinephrine; however, analysis of individual subjects revealed opposing responses of this subset. The T4:T8 ratio was 2.19 before injection, declined to 1.56 at 60 min, then increased to 3.10 2 hr postinjection. The percentage of natural killer/killer cells (HNK-1+) increased from a baseline of 15.5% before epinephrine injection to 29.6% at 30 min postinjection, then declined to 11.4% at 2 hr. Therefore, the administration of physiologic doses of epinephrine results in changes in the relative proportions of lymphocyte subsets in peripheral blood, in addition to reduced mitogen responsiveness as reported previously.     

Heterogeneous distribution and transmembrane signaling properties of lymphocyte function-associated antigen (LFA-1) in human lymphocyte subsets

The role of LFA-1, a member of the integrin supergene family, in intercellular adhesion, including lymphocyte-endothelial cell (EC) binding, has been established. We now demonstrate that differences in LFA-1 cell surface density are responsible for the variable adhesion efficiency of lymphocyte subsets to EC. Electrophoretic analysis revealed multiple glycosylated isoforms of both alpha and beta subunits, largely as a result of different degrees of sialylation, with variable expression among different lymphocyte subsets. Neuraminidase digestion before EC adhesion increased the binding efficiency of all lymphocyte subsets, although the relative increase in each subset was proportional to the initial LFA-1 sialic acid content. LFA-1 cross-linking resulted in phosphoinositide hydrolysis and a rise in [Ca2+]i when using anti-alpha but not anti-beta subunit antibodies. These findings indicate that the density of LFA-1 on lymphocyte subsets controls their adhesive properties, and that the LFA-1 alpha subunit has transmembrane signaling properties that may result in activation events after interaction with its natural ligands.     

Chronic metoclopramide treatment stimulates T lymphocyte proliferation in the spleen but not in the thymus.

The effect of chronic metoclopramide administration (for 10 days at a daily dose of 5 mg/kg body weight subcutaneously) on cell proliferation in spleen and in thymus was investigated. Cell proliferation was evaluated by the stathmokinetic method with the use of vincristine. It was found that metoclopramide administration results in a statistically significant increase in the value of the mean mitotic activity rate index (MMAR) of splenocytes in the areas around arteries. At the same time no statistically significant changes were demonstrated in the MMAR index values obtained for splenocytes present in the germinal centers of the spleen. No significant changes in the MMAR index could also be found for thymocytes.     

T and B lymphocyte populations of the spleen and thymus in normal and immunosuppressed BALB/c mice.

The antituinor agent 1,3 bis (2-chloroethyl)-1-nitrosourea (BCNU) has been studied in order to determine its effect on thymic and splenic T and B lymphocytes in normal and immunosuppressed BALB/c mice. Utilizing indirect immunofluorescence and lymphocyte proliferation studies we detected an initial reduction of splenic T and B cells as a result of the administration of an optimal dose, 30 mg/kg, of BCNU. The population dynamics of the thymic lymphocytes are totally different in their mitogenic reactivity than that of the splenic lymphocytes. An initial decline in the PHA and LPS-sensitive splenic lymphocytes of BCNU-treated mice was temporary. However, there was no return to normal levels detected for the Con A-sensitive splenic lymphocytes. On the other hand, the PHA-sensitive thymic lymphocytes of BCNU-treated mice not only failed to repopulate but were totally depleted by the tenth day.     

Impact of cadmium in T lymphocyte subsets and cytokine expression: differential regulation by oxidative stress and apoptosis

Cadmium (Cd), a possible human carcinogen is a potent immunotoxicant. In rodents it causes thymic atrophy and splenomegaly, in addition to immuno-suppression and modulation of humoral and/or cellular immune response. Oxidative stress and apoptosis appear to be underlying mechanism of Cd induced thymic injury. To understand the involvement of reactive oxygen species (ROS), intracellular glutathione (GSH) and apoptosis in modulation of T-cell repertoire, we studied the effect of Cd (10, 25 and 50 μM) on primary T lymphocytes of BALB/c mice at different time intervals (6, 12 and 18 h). We observed a dose and time dependent decline in CD4⁺/CD8⁺ ratio (a bio-indicator of immunotoxicity) as a result of significant suppression of CD4⁺ subsets (helper T-cells) and enhancement in CD8⁺ cells (cytotoxic T-cells) At the same time, the CD4⁺CD8⁺ (DP) cell population was lowered while the CD4⁻CD8⁻ (DN) cells were increased. The oxidative stress and apoptotic data revealed almost similar ROS generation in both CD4⁺ and CD8⁺ cells, but relatively more marked GSH depletion and apoptosis in CD4⁺ than in CD8⁺ population. On further analysis of CD4⁺ T-subsets, cytokine release (IL-2 and IFNγ) by Th 1 cells and IL-4 by Th 2 cells were shown to be significantly suppressed in a dose responsive manner. The highest inhibition was observed in IFNγ, then IL-2 followed by IL-4. In conclusion, our data demonstrates that T-cell apoptosis by Cd, more in CD4⁺ than in CD8⁺ cells appear related to higher depletion of intracellular glutathione. Th 1 cells of CD4⁺ sub-population are more responsive to Cd than Th 2, leading to higher suppression of IL-2 and IFNγ than IL-4 and hence, the study unravels to some extend, the underlying events involved in Cd immunotoxicity.     

Effects of cadmium on lymphocyte activation

The effects of cadmium (Cd) on phytohemoagglutinin or phorbol myristate acetate-induced lymphocyte activation were investigated and a dose-dependent inhibition of cell proliferation was found. Kinetic studies revealed that the Cd-sensitive step is an early event of T cell stimulation. Failure of IL2 secretion and reduction of IL2 receptor expression in the Cd-treated cells are also reported. Regardless of which mechanism is responsible for Cd effects, our studies show that the inhibition of lymphocyte activation is associated with reduced [3H]phorbol dibutyrate binding to Ca2+-phospholipid-dependent protein kinase and altered breakdown of phosphatidylinositols. Thus, Cd interferes with two biochemical events which play a critical role in lymphocyte signal transduction and activation.     

Immunoendocrine interrelationship--effect of ovariectomy on spleen and thymus in mouse.

Increase in the weights of spleen were observed 15 days after ovariectomy in adult as well as immature mice. However, no corresponding change was recorded in the splenocyte count. Morphological alterations in the shape of germinal centres was noted after ovariectomy in adult and immature mice. Increase in weight of the thymus could be demonstrated in adult mice only, with a concomitant enlargement of cortical and medullary region.     

Activity and distribution of biogenic amines in thymus and spleen structures following administration of iso- and heterologous erythrocytes

It was found that injection of heterological erythrocytes caused as soon as in 15 minutes displacement of noradrenaline from the efferent nerve endings and an essential re-building of metabolism of the central follicular cells and monoamine containing cells of the spleen marginal sinus, cortical fluorescent cells and mast cells of the thymus. Inversion of the medullary substance was revealed in the thymus.     

Effect of pesticide bendiocarbamate on distribution of acetylcholine- and butyrylcholine-positive nerves in rabbit's thymus

Many pesticides used in agriculture have a negative effect on organisms. The group of hazardous pesticides includes the cholinesterase inhibitor bendiocarbamate. According to literature, bendiocarbamate has relatively low toxicity in mammals and vertebrates in general, since it does accumulate in their tissues and the cholinesterase activity returns to norm within 24 h after acute exposure. The present study focused on the influence of bendiocarbamate on rabbit thymus after its administration at a dose of 5 mg/kg body weight (BW) for the period of 3 months. The thymus was observed for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)-positive nerve fibers visualized by histochemical methods. Microscopic findings of BuChE-positive nerve fibers show the same density and the topography by the experimental and the control animals. On the other hand, AChE-positive nerve fibers in experimental animals after administration of bendiocarbamate is only poorly identified, suggesting that bendiocarbamate inhibits AChE but not BuChE.     

Effects of labour and medication on major lymphocyte subsets in cord

It is envisaged that flow cytometric analysis of lymphocyte subsets in cord blood may be used as a biomarker for effects on the immune system of exposure to environmental factors. In order to investigate the possible application of this parameter, we first studied the effects of other factors that may influence the outcome of subset analysis in cord blood. FACS analysis was performed in 112 pairs of umbilical cord blood and of peripheral maternal blood sampled at labour. Whereas in maternal blood no statistically significant effects of medication during labour on T lymphocyte numbers and NK cells were found, in oxytocin and in oxytocin and prostaglandin treated mothers B cell numbers showed a statistically significant increase. In cord blood, the course of labour and or medication during labour were identified as the most important factors determining distribution of major lymphocyte subsets. In cord blood after deliveries without medication or after neuroplegic analgesia NPA, the mean percentage of cord blood T lymphocytes CD3 was highest 59 and that of NK lymphocytes CD3- CD16 56 lowest 20 . The mean percentage of T lymphocytes was significantly lower 52 and that of NK lymphocytes higher 28 in cord blood where deliveries were done under NPA in combination with infusion of oxytocin. The combination of NPA with oxytocin and induction of labour by prostaglandin E2 led to a further reduction of T lymphocytes and an increase of NK cells 39 and 38 respectively. The changes in ratio of T and NK lymphocytes were due both to decreasing absolute counts of T lymphocytes and increasing counts of NK lymphocytes. Thus, the effects of labour and or medication during labour must be taken into account when this parameter is applied as a potential biomarker of effects of environmental factors on the immune system.